Analysis of Adherence of Phenotypically Non-Serotypeable Aggregatibacter actinomyctemcomitans Isolates
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Aggregatibacter actinomycetemcomitans is a Gram-negative bacterium associated with aggressive forms of periodontitis. There are six different serotypes, a-f, of this species where each serotype expresses a serotype-specific polysaccharide antigen (SPA). One virulence property of A. actinomycetemcomitans is its adhesion capability to host sites, which is crucial for its pathogenicity. In this study we have tested the hypothesis that expression of the SPA may contribute to adherence of A. actinomycetemcomitans cells to abiotic surfaces. For this, we have compared the adherence and biofilm formation of strains of serotype a, b, c, and f, with derivatives of the same serotypes that had spontaneously lost their ability to express SPA. To minimize fimbriae-mediated adhesion, smooth colony variants, with afimbrial bacterial cells were first obtained of all the originally rough A. actinomycetemcomitans strains by repeatedly passages on blood agar. Microscopy analysis of Gram-, crystal violet, and ethidium bromide stained biofilms of smooth colony type strains in cell culture plates and glass tubes revealed no apparent difference in adherence, suggesting that the SPA did not act as an adhesin. Comparing adherence of the rough colony type strains revealed that the serotype f strain not expressing the SPA adhered less efficiently than the serotypeable f strain. This appeared to be due to increased auto-aggregation. To conclude, SPA expression seemed not to cause increased adherence of A. actinomycetemcomitans cells, whereas loss of SPA expression in some rough strains may generate a highly auto-aggregating phenotype.
Place, publisher, year, edition, pages
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:umu:diva-113671OAI: oai:DiVA.org:umu-113671DiVA: diva2:888107